Myocarditis Flashcards
(23 cards)
What is myocarditis?
An inflammatory process that may include the myocytes, interstitium, or the vascular tree
Myocarditis can be triggered by infectious agents (viral, bacterial, protozoal) or non-infectious factors (drugs, metabolic issues, toxins, heat).
What is the gold standard for diagnosing myocarditis?
Endomyocardial biopsy
Focal myocarditis may still be missed due to small sample size.
What are indicative signs of myocarditis?
Increased cTnI + cardiac arrhythmias in absence of readily identifiable cause
cTnI levels >10-100x reference interval are commonly observed in myocarditis.
What drug can cause myocarditis?
Doxorubicin
Certain medications like doxorubicin can contribute to the development of myocarditis.
What supportive findings can indicate myocarditis?
- Leukocytosis or eosinophilia
- Elevated cTnI
- Blood cultures for bacteremia
- Viral + rickettsial testing
- Serology + rising titer for T. gondii, N. caninum, T. cruzi
- CHF or cardiomegaly
- ventricular arrhythmias or conduction disturbances
- systolic dysfunction
- Immunohistochemistry or electron microscopy for N. caninum
- Histopathology showing myocyte necrosis or degeneration
These findings help in confirming the diagnosis of myocarditis.
What does elevated cardiac troponin I indicate in the context of myocarditis?
Myocardial cell damage
Elevated levels of cardiac troponin I are a sign of injury to the heart muscle.
What are common ECG findings in myocarditis?
- ventricular arrhythmias
- conduction disturbances
ECG changes can vary widely among patients with myocarditis.
What histopathological findings are associated with myocarditis?
Myocyte necrosis, degeneration, or both associated with an inflammatory infiltrate
These findings are crucial for confirming the diagnosis of myocarditis during histopathological examination.
Name 4 viral causes of myocarditis in dogs and 1 in cats
Dogs:
1. Parvovirus
2. Canine adenovirus type I
3. Distemper
4. West Nile virus
Cats:
1. FIV
Parvovirus can lead to fulminant CHF if maternal antibodies are absent.
What are the characteristics of Chagas Disease?
Protozoal infection caused by Trypanosoma cruzi, leads to DCM, transmitted via insect vector (Reduviidae), and has acute (R-CHF) and chronic syndromes (Nervous system damage: ataxia, weakness)
Reservoir hosts: rodents, racoons, opposums, dogs, cats, humans
geography: Texas, Louisiana
Diagnosis: rising titers
Acute symptoms include right-sided heart failure; chronic stage may show no clinical signs for months.
Which parasite is associated with myocarditis in canines?
Toxoplasma gondii (Bradyzoites encyst in canine myocardium –> cysts rupture –> myocardial necrosis + hypersensitivitiy reactions)
Neospora caninum (heart, CNS, muslces)
Trichinella spiralis
Can encyst in myocardium, leading to chronic infection and potential myocardial necrosis.
What are common bacteria causing myocarditis in dogs?
Staphylococcus
streptococcus
Others:
Citrabacter koseri (opportunistic in immunosuppressed)
Bacillus piliformins (Tyzzer disease)
Rickettsial (R. rickettsii, Ehrlichia canis, Bartnoella spp., Borrelia burgdorferi)
Bacteremia or sepsis can lead to myocarditis.
Name 7 causes of non-infectious myocarditis
- Doxorubicin toxicity (dose-dependent, irreversible)
- allergic reactions
- systemic disease
- physical agents (radiation, heat stroke)
- pheochromocytoma (reversible in people)
- catecholamine toxicity
- immune-mediated polymyositis
Each of these causes can lead to myocardial damage.
Why should digoxin be avoided in myocarditis treatment?
Increased expression of proinflammatory cytokines and increased mortality (experimental)
Digoxin may worsen inflammation and has been shown to have negative outcomes in experimental settings.
What type of therapy may be beneficial in an experimental model of myocarditis?
Interferon therapy
Further research is needed to establish its efficacy in clinical settings.
Outline the treatment for myocarditis
- Supportive care
- Preload reduction (furosemide) + afterload reduction (ACE inhibitors) in CHF
- IV inotrops if systolic dysfunction
- Elimination of unneccessary medication (possible allergic myocarditis)
- Immunosuppression in autoimmune disease
- Interferon therapy? –> beneficial in experimental model
- Empiric ABs if bacterial
- Doxycycline for rickettsial disease
What are the most common clinical signs of myocarditis in dogs (Lakhdhir et al JVC 2020)?
Lethargy and hyporexia
gastrointestinal signs
tachypnea
fever
heart murmur
Over 2/3 of dogs exhibited lethargy and hyporexia; fever was present in 21% (> 102.5°F), and heart murmur in 19% of cases.
What was the median cardiac troponin I (cTnI) level in dogs with myocarditis?
12.2 ng/mL; range 0.2-808 ng/mL
Elevated cTnI indicates myocardial injury, with all measured dogs showing elevated levels.
What percentage of dogs with myocarditis exhibited arrhythmias on ECG (Lakhdhir et al JVC 2020)?
91%
Tachyarrhythmias were more common than bradyarrhythmias, with ventricular tachycardia being the most frequent (46%).
What echocardiographic findings were observed within 24 hours in dogs with myocarditis (Lakhdhir et al JVC 2020)?
Decreased systolic function, left ventricular dilation, changes in echogenicity of the myocardium, pericardial effusion (16%)
These findings reflect significant cardiac dysfunction and potential fluid accumulation.
What was the most common infectious cause of myocarditis in dogs (Lakhdhir et al JVC 2020)?
Bacterial sepsis
This occurred in 9 dogs and was the most frequently identified infectious agent.
What was the median survival time (MST) for dogs with myocarditis (Lakhdhir et al JVC 2020)?
4 days
64% of cases were related to patient death, with only 58% surviving beyond 2 weeks.
What percentage of dogs with myocarditis survived beyond 2 weeks (Lakhdhir et al JVC 2020)?
58%
Among the dogs that survived, the median survival time was only 81 days.
